Abstract

Hydrogels represent a class of materials suitable for numerous biomedical applications such as tissue engineering and drug
delivery. Hydrogels are by definition capable of absorbing large amount of fluid, making them adequate for cell seeding and
encapsulation as well as for implantation because of their biocompatibility and excellent diffusion properties. They also
possess other desirable properties for fundamental research as they have the ability to mimic the basic three‐dimensional
(3D) biological, chemical, and mechanical properties of native tissues. Furthermore, their biological interactions with cells
can be modified through the numerous side groups of the polymeric chains. Thus, the biological, chemical, and mechanical properties,
as well as the degradation kinetics of hydrogels can be tailored depending on the application. In addition, their fabrication
process can be combined with microtechnologies to enable precise control of cell‐scale features such as surface topography
and the presence of adhesion motifs on the hydrogel material. This ability to control the microscale structure of hydrogels
has been used to engineer tissue models and to study cell behavior mechanisms in vitro. New approaches such as bottom‐up and directed assembly of microscale hydrogels (microgels) are currently emerging as powerful
methods to enable the fabrication of 3D constructs replicating the microenvironment found in vivo. WIREs Nanomed Nanobiotechnol 2012, 4:235–246. doi: 10.1002/wnan.171

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Hydrogel materials have the ability to recapitulate the basic properties of the extracellular matrix (ECM) found in vivo. They are particularly suitable for cell encapsulation, making them an attractive material for biomedical applications.

Tissue engineering and regenerative medicine. Cells are harvested from the patient, expanded in culture (1) and seeded into a porous scaffolding material (2). The cell‐seeded scaffold (3) can then be implanted into the patient to restore tissue function (4).

Evolution of the mechanical properties of a cell‐laden hydrogel as a function of time. The cell‐seeded scaffolding material is degraded by the cells, which reduce its mechanical properties. In parallel, cells produce extracellular matrix (ECM) resulting in tissue regeneration and an increase in the mechanical properties of the engineered tissue. The intersection between the curves representing the degradation kinetics of the biomaterial and the ECM synthesis by the cells need to remain over the threshold required for adequate tissue function throughout the regeneration process.